The transportation share of U.S. energy consumption is around 28% (or 28.4 quadrillion Btu) with petroleum accounting for 96% of this amount (every day, the U.S. consumes about 13 million barrels of petroleum for transportation). Engine and drive-train friction accounts for 10-15% of the fuel's total energy used in current vehicles, which translates to about 1.3 to 2 million barrels of petroleum/day lost to friction alone. Furthermore, a significant amount of energy is spent to remanufacture and/or replace worn parts in these systems. In short, the energy efficiency, durability, and environmental compatibility of all motorized and mechanical devices are closely related to the effectiveness of the lubricants on rolling, rotating, and sliding contact surfaces. Poor or inefficient lubrication results in higher friction and severe wear losses, which in turn adversely impacts performance and durability [1]. In addition, lubricants can include additives such as viscosity index improvers, anti-oxidant agents, anti-corrosion agents, wear-protection agents, acid neutralizers, dispersants and the like to provide beneficial properties.
The energy efficiency, durability, and environmental compatibility of all kinds of moving mechanical systems (including engines) are closely related to the effectiveness of the lubricants being used on their rolling, rotating, and sliding surfaces. Therefore, lubricants play a vital role in machine life, efficiency, and overall performance. Poor or inefficient lubrication always result in higher friction and severe wear losses, which can in turn adversely impact the performance and durability of mechanical systems. In particular, progressive wear due to inadequate lubrication is one of the most serious causes of component failure. Inadequate lubrication can also cause significant energy losses in the above-mentioned industrial systems mainly because of high friction.
Currently, there are numerous solid lubricants available at sizes ranging from 1 nm to more than 500 nm in powder forms. The finer solids (i.e. 1 to 30 nm range) are mostly made of nanostructured carbons, like C60, nano-tubes, nano-fibers, and nano-onions while intermediate range lubricants (30 to 100 nm) are made of inorganic solids, such as MoS2, WS2, h-BN and pure metals (like gold, silver, tin, bismuth, etc.). WS2 is synthesized typically in the form of fullerene-like particles and hence it is often referred to as inorganic fullerene or, IF. Most of these materials are manufactured using a bottom-up approach involving multi-step chemical synthesis routes (e.g. gas phase chemical processing, combustion synthesis, sonochemistry, etc.) and the uses of environmentally unsafe chemicals. Many current processes also generate large amounts of toxic by-products to deal with after the manufacturing.
There is an ongoing need for new lubricant compositions that are environmentally friendly or benign, and which provide reduced friction and wear. The present invention addresses this need.